Gear systems with variable speed drive

ABSTRACT

An epicyclic gear system includes an input sun gear configured to receive rotational input from a turbine of a turbo charger. A first set of planet gears is distributed around and meshes with the input sun gear. A carrier holds the first set of planet gears and defines a rotational axis about which the carrier rotates. A second set of planet gears is mounted to the carrier. An output sun gear is included, wherein the second set of planet gears are distributed around and mesh with the output sun. The output sun gear is configured to deliver rotational power to an internal combustion engine. The carrier is configured to selectively be driven by a variable speed drive to regulate output to the output sun over a range of input rotational speeds of the input sun gear.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 63/010,894, filed Apr. 16, 2020. The entire contents of which are incorporated herein by reference.

BACKGROUND 1. Field

The present disclosure relates to power transfer, and more particularly to transferring power within a power plant for aerospace applications.

2. Description of Related Art

Aircraft power plants, including turboshaft engines, turboprop engines, turbofan engines, hybrid-electric power plants, and the like, can have multiple sources of rotational power. For example in a hybrid-electric power plant there can be an internal combustion engine, one or more turbochargers, and one or more electric motors. One or more transmissions are needed to deliver the power from these sources of rotational power to an air mover such as a propeller.

The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for power transfer in hybrid-electric power plants such as for aerospace applications. This disclosure provides a solution for this need.

SUMMARY

An epicyclic gear system includes an input sun gear configured to receive rotational input from a turbine of a turbo charger. A first set of planet gears is distributed around and meshes with the input sun gear. A carrier holds the first set of planet gears and defines a rotational axis about which the carrier rotates. A second set of planet gears is mounted to the carrier. An output sun gear is included, wherein the second set of planet gears are distributed around and mesh with the output sun. The output sun gear is configured to deliver rotational power to an internal combustion engine. The carrier is configured to selectively be driven by a variable speed drive to regulate output to the output sun over a range of input rotational speeds of the input sun gear.

Each gear of the second set of planet gears can be on a common shaft with a respective one of the gears of the first set of planet gears so the first and second sets of planet gears rotate together about the rotational axis with rotation of the carrier. Each gear of the second set of planet gears can be rotationally fixed relative to the respective one of the planet gears of the first set of planet gears to rotate together around an axis of the respective common shaft as they also revolve around the rotational axis with rotation of the carrier.

The input sun gear can be smaller than the output sun gear. Each gear of first set of planet gears can be larger than each of the respective gears of the second set of planet gears. The system can be devoid of a ring gear surrounding and meshing with the first set of planet gears. The system can be devoid of a ring gear surrounding and meshing with the second set of planet gears.

The variable speed drive can be connected to drive the carrier with variable speed to regulate output to the output sun over a range of input rotational speeds of the input sun gear. The variable speed drive can be a hydraulic system. The variable speed drive can connect directly to drive the carrier without connecting to the carrier by way of a ring gear meshing with the first or second sets of planet gears.

The system can include the internal combustion engine connected to be driven by the output sun gear. The turbo charger turbine can be connected to the input sun gear to provide power to the internal combustion engine. One or more accessory gears can be operatively connected to the output sun gear to drive accessory devices. The variable speed drive can include an input gear operatively connected to the output sun gear to provide input drive to the variable speed drive. The input gear can be mounted to a bearing having a fixed outer race and an inner race that rotates with the input gear relative to the outer race. The variable speed drive can include an output gear operatively connected to drive the carrier, wherein the variable speed drive includes an internal mechanism configured to drive the output gear at a different speed from the input gear, and to vary the ratio of speed difference between the input gear and the output gear. The carrier can be mounted to a bearing having a fixed outer race and an inner race that rotates with the carrier relative to the outer race.

A method includes providing rotational power as input to an input sun gear and driving planet gears with the input sun gear, wherein the planet gears are operatively connected to a carrier to revolve around the input sun gear. The method includes controlling revolution speed of the carrier with a variable speed drive and providing rotational output power from the planet gears to an output sun gear, wherein the rotational output power is speed regulated by controlling revolution speed and direction of the carrier and variable speed drive.

Controlling revolution speed of the carrier with the variable speed drive can include driving the variable speed drive with at least one gear operatively connected to the output sun gear. The method can include varying output speed of the variable speed drive given a constant input speed to the variable speed drive. The method can include varying rotational direction of rotational output of the variable speed drive. Controlling revolution speed of the carrier with the variable speed drive can include altering speed of the carrier to maintain constant output speed of the output sun gear given variable input speed to the input sun gear.

These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:

FIG. 1 is a schematic perspective view of an embodiment of a system constructed in accordance with the present disclosure, showing the carrier and planet gears;

FIG. 2 is a schematic end view of the system of FIG. 1 , schematically indicating the meshing of the planet and sun gears;

FIG. 3 is a schematic view of the system of FIG. 1 , showing the turbine, internal combustion engine, and variable speed drive; and

FIG. 4 is a schematic side view of the system of FIG. 1 , showing the bearings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a system in accordance with the disclosure is shown in FIG. 1 and is designated generally by reference character 100. Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided in FIGS. 2-4 , as will be described. The systems and methods described herein can be used to transfer power between a turbine of a turbo charger and an internal combustion engine, e.g. in a hybrid-electric aircraft power plant. Any suitable internal combustion engine can be used, such as a gas turbine, spark ignited, diesel, rotary or reciprocating engine of any fuel type with a configuration of turbomachinery elements, selected from a group consisting of a turbocharger, turbo-supercharger, or supercharger and exhaust recovery turbo compounding, which is mechanically, electrically, hydraulically or pneumatically driven. An example of a rotary engine suitable for this application is disclosed in U.S. Pat. No. 10,145,291, the disclosure of which is herein incorporated by reference in its entirety.

The epicyclic gear system 100 includes an input sun gear 102 configured to receive rotational input from a turbine 104 (shown in FIG. 3 ) of a turbo charger. A first set of planet gears 106 is distributed around and meshes with the input sun gear 102. A carrier 108 holds the first set of planet gears 106 and defines a rotational axis A about which the carrier 108 rotates. A second set of planet gears 110 is mounted to the carrier 108. An output sun gear 112 (not shown in FIG. 1 , but see FIGS. 2-3 ) is included, wherein the second set of planet gears 110 are distributed around and mesh with the output sun 112, as schematically indicated in FIG. 2 . The output sun gear 112 is connected to deliver rotational power to an internal combustion engine 114, as shown in FIG. 3 and any other suitable accessories such as a variable speed drive 116 to supply power to the system 100. The carrier 108 is connected to selectively be driven by the variable speed drive 116 to regulate output to the output sun 112 over a range of input rotational speeds of the input sun gear 102.

Each gear 110 of the second set of planet gears 110 is on a common shaft 118 with a respective one of the gears 106 of the first set of planet gears 106 so the first and second sets of planet gears 106, 110 rotate together about the rotational axis A with rotation of the carrier 108. Each gear 110 of the second set of planet gears 110 is rotationally fixed relative to the respective one of the planet gears 106 of the first set of planet gears 106 to rotate together around an axis B of the respective common shaft 118 as they also revolve around the rotational axis A with rotation of the carrier 108.

The input sun gear 102 is smaller than the output sun gear 112. Each gear 106 of first set of planet gears 106 is larger than each of the respective gears 110 of the second set of planet gears 110. The system 100 is devoid of a ring gear surrounding and meshing with the first set of planet gears 106, or with the second set of planet gears 110.

The variable speed drive 116 is connected by an output gear train including output gears 122 to drive the carrier 108 with variable speed to regulate output to the output sun 112 (e.g. to keep the speed of the output sun 112 constant) over a range of input rotational speeds of the input sun gear 102 (e.g. as the speed of the turbine 104 of FIG. 2 varies). The variable speed drive 116 connect directly to drive the carrier 108 without connecting to the carrier 108 by way of a ring gear meshing with the first or second sets of planet gears 106, 110.

As shown in FIG. 3 , the turbo charger turbine 104 connects to the input sun gear 102 to ultimately provide power to the internal combustion engine 114, to which the turbo charger provides turbo charged aspiration. One or more accessory gears 124 can be operatively connected to the output sun gear 112 to drive accessory devices. The variable speed drive 116 is connected to a train of input gears 120 operatively connected to the internal combustion engine 114, e.g., by way of being connected to the output sun gear 112, to provide input drive to the variable speed drive 116. The variable speed drive 116 includes or connects to an output gear train of output gears 122 operatively connected to drive the carrier 108. The variable speed drive 116 is a hydraulic system that includes an internal mechanism 126 (schematically shown in FIG. 3 ) configured to drive the output gears 122 at a different speed from the input gears 120, and to vary the ratio of speed difference between the input gears 120 and the output gears 122. It is also contemplated that the variable speed drive 116 could include an output gear 122 driven by a battery powered electric motor, or any other suitable driving source, e.g., in lieu of the input gears 120. FIG. 3 schematically shows the flow of power from the internal combustion engine 114 to the input gears which provide power to the variable speed drive 116, and from the variable speed drive 116 to the carrier 108 through the output gears 122. The internal combustion engine 114 also provides power to the accessory gears 124, which are basically in parallel with the input gears 120, for driving other accessories.

With reference now to FIG. 4 , the carrier 108 is supported by a bearing 128 that has a fixed outer race and in inner race that rotates with the carrier 108 relative to the outer race. Similarly, the bearing 132 supporting one of the input gears 120 has a fixed outer race and in inner race that rotates with the input gear 120 relative to the outer race. The other bearings shown but not numbered in FIG. 4 can each have rotating inner and outer races.

A method includes providing rotational power as input to an input sun gear (e.g. input sun gear 102) and driving planet gears (e.g. planet gears 106, 110) with the input sun gear, wherein the planet gears are operatively connected to a carrier (e.g. carrier 108) to revolve around the input sun gear. The method includes controlling revolution speed of the carrier with a variable speed drive (e.g. variable speed drive 116) and providing rotational output power from the planet gears to an output sun gear (e.g. output sun gear 112), wherein the rotational output power is speed regulated by controlling revolution speed and direction of the carrier and variable speed drive.

Controlling revolution speed of the carrier with the variable speed drive can include driving the variable speed drive with at least one gear (e.g. input gears 120) operatively connected to the output sun gear. The method can include varying output speed of the variable speed drive given a constant input speed to the variable speed drive. The method can include varying rotational direction of rotational output of the variable speed drive, i.e., the variable speed drive can change rotating the output gears 122 back and forth the between clockwise and counterclockwise. Controlling revolution speed of the carrier with the variable speed drive can include altering speed of the carrier to maintain constant output speed of the output sun gear given variable input speed to the input sun gear.

The methods and systems of the present disclosure, as described above and shown in the drawings, provide for transfer of power between the turbine of turbo charger and an internal combustion engine, with variable speed capability. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure. 

What is claimed is:
 1. An epicyclic gear system comprising: an input sun gear configured to receive rotational input from a turbine of a turbo charger; a first set of planet gears distributed around and meshing with the input sun gear; a carrier holding the first set of planet gears and defining a rotational axis about which the carrier rotates; a second set of planet gears mounted to the carrier; and an output sun gear, wherein the second set of planet gears are distributed around and mesh with the output sun, wherein the output sun is configured to deliver rotational power to an internal combustion engine, the carrier being configured to selectively be driven by a variable speed drive to regulate output to the output sun gear over a range of input rotational speeds of the input sun gear.
 2. The system as recited in claim 1, wherein each gear of the second set of planet gears is on a common shaft with a respective one of the gears of the first set of planet gears so the first and second sets of planet gears rotate together about the rotational axis with rotation of the carrier.
 3. The system as recited in claim 2, wherein each gear of the second set of planet gears is rotationally fixed relative to the respective one of the planet gears of the first set of planet gears to rotate together around an axis of the respective common shaft as they also revolve around the rotational axis with rotation of the carrier.
 4. The system as recited in claim 1, wherein the input sun gear is smaller than the output sun gear.
 5. The system as recited in claim 1, wherein each gear of first set of planet gears is larger than each of the respective gears of the second set of planet gears.
 6. The system as recited in claim 1, wherein the system is devoid of a ring gear surrounding and meshing with the first set of planet gears.
 7. The system as recited in claim 1, wherein the system is devoid of a ring gear surrounding and meshing with the second set of planet gears.
 8. The system as recited in claim 1, further comprising the variable speed drive connected to drive the carrier with variable speed to regulate output to the output sun over a range of input rotational speeds of the input sun gear.
 9. The system as recited in claim 8, wherein the variable speed drive is a hydraulic system.
 10. The system as recited in claim 8, wherein the variable speed drive connects directly to drive the carrier without connecting to the carrier by way of a ring gear meshing with the first or second sets of planet gears.
 11. The system as recited in claim 1, further comprising the internal combustion engine connected to be driven by the output sun gear.
 12. The system as recited in claim 1, further comprising the turbo charger turbine connected to the input sun gear to provide power to the internal combustion engine.
 13. The system as recited in claim 1, further comprising one or more accessory gears operatively connected to the output sun gear to drive accessory devices.
 14. The system as recited in claim 1, wherein the variable speed drive includes an input gear operatively connected to the output sun gear to provide input drive to the variable speed drive.
 15. The system as recited in claim 14, wherein the input gear is mounted to a bearing having a fixed outer race and an inner race that rotates with the input gear relative to the outer race.
 16. The system as recited in claim 14, wherein the variable speed drive includes an output gear operatively connected to drive the carrier, wherein the variable speed drive includes an internal mechanism configured to drive the output gear at a different speed from the input gear, and to vary the ratio of speed difference between the input gear and the output gear.
 17. The system as recited in claim 1, wherein the carrier is mounted to a bearing having a fixed outer race and an inner race that rotates with the carrier relative to the outer race.
 18. A method comprising: providing rotational power as input to an input sun gear; driving planet gears with the input sun gear, wherein the planet gears are operatively connected to a carrier to revolve around the input sun gear; controlling revolution speed of the carrier with a variable speed drive; and providing rotational output power from the planet gears to an output sun gear, wherein the rotational output power is speed regulated by controlling revolution speed and direction of the carrier and variable speed drive.
 19. The method as recited in claim 18, wherein controlling revolution speed of the carrier with the variable speed drive includes driving the variable speed drive with at least one gear operatively connected to the output sun gear.
 20. The method as recited in claim 19, further comprising varying output speed of the variable speed drive given a constant input speed to the variable speed drive.
 21. The method as recited in claim 20, further comprising varying rotational direction of rotational output of the variable speed drive.
 22. The method as recited in claim 20, wherein controlling revolution speed of the carrier with the variable speed drive includes altering speed of the carrier to maintain constant output speed of the output sun gear given variable input speed to the input sun gear. 